<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        var name = "window";
        var person = {
            name: "person",
            sayName: function () {
                console.log(this.name);
            },
            waitAndSay: function () {
                setTimeout(function () {
                    console.log(this.name);
                }, 1000);
            }
        };

        person.sayName();   // person
        person.waitAndSay();  // window

        var otherSay = person.sayName
        otherSay();  // window    大叔大婶d
    </script>
</body>

</html>